Would any of these work for you, used with one or more USB flash keys (or even an iPod) in place of the laptop ?
Depends on how good the user interface on them is. My concern with any non-laptop solution is ease of finding/browsing songs. Nothing beats a full-size keyboard, a decent-size display and a well designed GUI.
Based on Rob's demos from the 2006 Empeg Meet, the GUI looked really well done. And you can plug a USB keyboard into the Director (probably the others, too).
They did look very slick at the meet. And are Linux based.
cheers